This invention relates to a data processing device, and particularly to a data processing device for receiving a degraded data stream and generating therefrom an estimate of the original, non-degraded, data stream.
Digital data that is transmitted over some link, be it physical or wireless, will usually be degraded to some extent. For example, noise or electromagnetic interference can affect the data such that errors will be present in the received data. The degradation may affect the amplitude of the data and/or the timing of the data. In serious cases, degradation of the amplitude of the data may result in a “high” level signal being interpreted as a “low” level signal. Timing errors, such as clock jitter, can cause a loss of synchronization.
Accordingly, digital data receiving devices often use data and timing recovery circuits that attempt to recover the originally transmitted data. Conventional recovery circuits, such as the wireless local area network (LAN) chip WL102, generally use edge detection techniques combined with a state machine for detecting the start of a data packet. State machines have disadvantages since the ability to identify a good data packet relies on the state machine being in a correct initial state.
It is desirable to provide a reliable digital data processing device for recovering good data packets from a received degraded data stream.